Each of the first four volumes provides 25 probes with easy-to-follow steps for uncovering and addressing students’ ideas by promoting learning through conceptual change instruction. Probes cover topics such as physical, life, and Earth and space science; the nature of science; and unifying themes. Each volume on page 23 provides topic-specific probes. These invaluable books include teacher materials that explain content, identify links to standards, and suggest grade-appropriate ways to present materials so students learn the concepts accurately. Teachers, professional development coordinators, and college science and preservice faculty will find these resources essential and exciting.
The purpose of this assessment probe is to elicit students’ ideas about decay and decomposers. The probe can be used to determine whether students recognize the need for a biological agent to break down once-living material as it uses it for energy.
Decay, decomposers, decomposition, microbes
The best response is Selma’s: I think small organisms use it for energy and building material. Rotting, or decay, is a natural recycling process in which the material of once-living things is broken down and released into the environment to be reassembled and used again by other organisms or incorporated into the physical environment. Natural decay does not happen without a biological agent. Dead organisms or parts of once-living organisms are broken down by biological agents, called decomposers. The material of the apple that is no longer part of the living tree is a source of food for decomposers. This food provides the energy and building material they need to live, grow, and reproduce. Decomposers include worms, insects, fungi, and bacteria. Most decay is the result of action by microorganisms (bacteria and some fungi). Decomposers are found in large numbers almost everywhere in an ecosystem, including in air, land, and water. They are prevalent in the upper layers of most soils. Fungal spores and bacteria also make up particulate matter in the air. The factors that support decay are the factors that support microbial growth, such as warmth and moisture.
During the elementary grades, children build an understanding of biological concepts through directly observing phenomena, such as the rotting apple. Students identify factors that promote decay and observe the changes that happen to a decomposing object over time. They develop a basic understanding of decomposers and the decay process, beginning with macroscopic organisms they can readily observe, such as worms, beetles, mushrooms, and molds.
Middle School Students
In the middle school grades, students become familiar with the beneficial role of bacteria in ecosystems. They expand their understanding of decomposers and decay to include microorganisms and recognize their essential role in the decomposition process as matter recyclers. They are introduced to ideas about nutrition, matter, and energy flow, and they identify the relationships between organisms in a food web, including decomposers.
High School Students
In high school, students approach decomposition from a molecular view, including the assortment of complex biological processes involved in breaking down once-living material. They recognize the role of decomposers in cycling atoms and molecules throughout the living and nonliving components of Earth’s biosphere. They connect the natural process of biodegradation to human engineered systems that solve problems of buildup of dead material and metabolic wastes.
The answer to this probe deliberately uses the idea that small organisms use the apple for energy and building material rather than directly mentioning food, but it does not include the idea of breaking it down into simpler substances since students can choose that response to match their notion of rotting, yet not understand the decay process. When food is used in the correct response, students are apt to choose it without considering the idea of decay. To students, an apple is food and other organisms eat apples. Because the idea of a source of energy is introduced in upper elementary school, we choose to use energy in this answer rather than food. However, if you are using this probe with younger students, grades K–2, you may wish to substitute food for energy and building material and remove Felicia’s response. This probe can also be used with a prop. Show a rotted apple (preferably one that has been on the ground) and a fresh one. Other material can be substituted for the apple (e.g., pumpkins, rotted logs, dead leaves). Avoid bringing in dead and decaying animals or decayed logs with exposted fungi that can release spores.
K–4 The Characteristics of Organisms
K–4 Organisms and Their Environments
5–8 Populations and Ecosystems
9–12 The Interdependence of Organisms
9–12 Matter, Energy, and Organization in Living Systems
K–2 Flow of Matter and Energy
K–2 Constancy and Change
3–5 Interdependence of Life
3–5 Flow of Matter and Energy
6–8 Interdependence of Life
6–8 Flow of Matter and Energy
9–12 Flow of Matter and Energy
American Association for the Advancement of Science (AAAS). 1993. Benchmarks for science literacy. New York: Oxford University Press.
Driver, R., A. Squires, P. Rushworth, and V. Wood-Robinson. 1994. Making sense of secondary science: Research into children’s ideas. London and New York: RoutledgeFalmer.
Hogan, K. 1994. Eco-inquiry: A guide to ecological learning experiences for the upper elementary/ middle grades. Millbrook, NY: Institute of Ecosystem Studies.
Keeley, P. 2005. Science curriculum topic study: Bridging the gap between standards and practice. Thousand Oaks, CA: Corwin Press.
National Research Council (NRC). 1996. National science education standards. Washington, DC: National Academy Press.